The present disclosure relates to an optical scanning device using a multi-beam-type light source for scanning a scanned surface, and to a beam adjustment method for use therein.
An image forming apparatus such as a laser printer or a copier includes an optical scanning device for forming an electrostatic latent image by scanning a circumferential surface (scanned surface) of a photoconductor drum. The optical scanning device includes: a light source for emitting a light beam; a deflector for deflecting the light beam; an incident optical system for causing the light beam to be incident on a reflection surface of the deflector; and a focusing optical system for causing the deflected light beam (scanning light beam) to focus on the scanned surface. The incident optical system includes, as optical elements, a collimator lens and a cylindrical lens, wherein the collimator lens converts diffused light beams to parallel light beams, and the cylindrical lens converts the parallel light beams to line-like light beams and focuses the light beams on the reflection surface of the deflector.
A multi-beam-type light source that emits a plurality of light beams may be used as the light source. In addition, a function-integrated-type optical element that has both a collimator lens function and a cylindrical lens function may be used as an optical element of the incident optical system. In the case where the function-integrated-type optical element is used, during an optical adjustment performed when the optical scanning device is assembled, the beam diameters in the main scanning direction and the sub scanning direction cannot be adjusted independently of each other. According to a known conventional method for coping with the problem, the beam diameters are adjusted by integrally moving the light source and the function-integrated-type optical element in the optical axis direction in the state where the positional relationship between the light source and the function-integrated-type optical element is established.